Henry grafton



(No Model.)

H. GRAFTON.

KEYING WHEELS.

No. 408,835. Patented Aug. 13, 1889.

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UNITED STATES PATENT ()EFICE.

HENRY GRAFTON, OF OHANCERY LANE, COUNTY OF MIDDLESEX, ENGLAND.

KEYING WHEELS.

SPECIFICATION forming part of Letters Patent No. 408,835, dated August 13, 1889. Application filed August 30, 1888. Serial No. 284,179. (No model.)

To all whom it may concern.-

Be it known that I, HENRY GRAFTON, engineer, of Chancery Lane, in the county of Middlesex, England, a subject of the Queen of Great Britain, have invented certain new and useful Improvements in Keying WVheels and other Parts of Machinery to Shafts and Axles, of which the following is a specification. 1

My invention relates to the keying of wheels and other parts of machinery upon circular shafts or axles; and it has for its object to obviate the difficulty of fitting and the defects in working inherent to the ordinary mode of keying.

Reference is to be had to the accompanying drawings, forming part of this specification, in which Figure 1 represents a cross-section of a shaft and key with a portion of the surrounding hub or boss of the wheel or other part to be keyed, the key being of the ordinary form and in the usual position. Fig. 2 is a similar View illustrating the improved mode of keying of this invention. Fig. 3 is a similar view showing a modification of the form of key; and Fig. L is a perspective view of a taper key of square section, the amount of taper relatively to the length of the key being greatly magnified.

The same letters of reference indicate the same parts in all the figures.

In the ordinary mode of keying with a driven key, as represented in Fig. 1, it is usual to make the key-seat in the shaft A and that in the hub or boss B (of the wheel or other part to be keyed) in the form of threesided grooves a 7) c (l e fthe sides a d perpendicular to and the sides 6 h f 0 parallel to a radius g h of the shaft intersecting the axis of the key.

It is usual to make the key-seat- (Z c f in the hub or boss of gradually varying depth and the key 0 of wedge shape to correspond, this tapering of the key in the direction of its thickness being known as the draft, while the key-seats are of uniform width-that is to say, the sides 6 f and b c are parallel, as are likewise the sides of the key.

In fitting a key to such a keyway it requires considerable skill to make the key a good fit between the parallel sides Z) c and e f of the keyways, such as is necessary to prevent the key working loose. Assuming the ordinary key to be well fitted and not driven up excessively, and assuming the shaftA to be driving the hub B in the direction of the arrow, Fig. 1, it will be obvious that the whole of the driving strain transmitted through the key will lie between the two lines 11 k, the diagonal between the opposite corners representing the line of force; but as the sides of the key and keyways are parallel it is impossible to make the key fit so tightly on the sides as it does on the top and bottom, and therefore in a sunk key fitted in the ordinary way the metal of the key is not compressed in the direction in which the Working strain comes or should come upon it, and consequently even in a wellfitted key the key is not entirely free from shake in consequence of the elasticity of the metal permitting it to yield to the strain.

My invention consists in the combination, with a shaft or axle and with a hub or boss, each having a key-seat, of a driven key having four acting sides and having draft upon those sides, these four acting sides fitting tightly between the sides of the key-seats and forming opposite dihedral angles, which are met at their apexes by the circle of the shaft, each two opposite acting sides of the key being bisectable (in the direction of their Width) by a common normal.

It is essential that the opposite sides of the key which transmit the strain shall be parallel transversely and shall be perpendicular to and be bisected transversely by the center line of strain passing from the shaft to the hub or boss, or vice versa. The preferred (because the simplest) sectional form of the key is therefore square; but the above conditions will be fulfilled by a key of hexagonal section. In practice a key of square section would be used in key-beds of semisquare form,as represented in Fig. 2, the key having four acting sides and having draft on these four sides. Said four acting sides fit tightlybetween the sides of the key-seats and form opposite dihedral angles, which are met at their apexes by the circle of the shaft. The

two opposite acting sides of the key are bisectable (in the direction of their width) by a common normal. The coincidence of the circumference of the shaft with the angles of the key is true only at one point. in the length of the key in consequence of the draft or taper form of the key, and this preferably at or about the middle of its length.

A square key fitted as above described obviously equally well adapted to transmit strains in either direction of rotation, as it fits equally tight on all four sides, as above mentioned. The key, although preferably of square section, is not necessarily so, and is not necessarily four-sided, although only four sides would be effective. For instance, it might be hexagonal, as in Fig. 3. The key would only fit the seats in the sides adjacent to the angles intersected by the circle of the shaft, a slight amount of clearance being left at the remaining sides. The remaining sides, which are not met by the circumference of the shaft, do not act in transmitting strain. The opposite sides of the key that are met by the circumference of the shaft form opposite dihedral angles and the opposite acting faces of the key are bisectable by a common normal. Both of the seats are of approximately semi-hexagonal form, as shown.

Generally the key-seat in the shaft would be of uniform depth, and the seat in the hub or boss would be of gradually varying depth; but under certain circumstances these conditions might be reversed, the key being in any case tapered in the direction of itslength or having draft on all of its sides. The amount of draft necessary will therefore be less than usual.

Among the advantages of this improved mode of keying over the ordinary mode illustrated in Fig. 1 may he mentioned that. it is only requisite in cutting the key-seats to remove half the usual amount of metal, as the key would, other things being equal, be of the same dimensions measured diametrically from corner to corner as the ordinary key is measured across its sides. This is shown in Fig. 2, in which the dotted lines represent the seats for the ordinary key. The same tool will out various sizes of grooves of the forms shown, and such grooves are much more easily cut, and the key maybe fitted thereto with much greater facility. The key, when driven up, must necessarily bear on four sides, and consequently an initial strain will be put on the metal in whichever direction the working strain may come upon it. Therefore the key will not be liable to work loose when subjected to reverse strain.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is The combination, with a shaft or axle and with a hub or boss, each having a key-seat, of a driven key having four acting sides and having draft upon those sides, those four acting sides fitting tightly between the sides of l IENRY GRAFTON.

\Vitnesses:

\VAmnn J. SKERTEN, l7 Gmcechm'cla.Street, London, E. U.

CIIAS. BERKLEY HARRIS, 1V o/ary Public, London. 

